When ice fishing an opening is cut through many feet of ice. A line is then inserted through the opening in order to catch fish feeding in the depths below. Frequently, as the fisherman hauls a fish he has hooked up through the ice opening, a portion of the fish in which the hook is embedded (such as the lip, gill, or jaw) will break and the fish will escape. Other times, with the change in pressure as the fish comes to the surface, an expansion of the air sacs of the fish dislodges the hook.
In most cases where the fish escapes it is injured to the point where it can no longer survive.